1. Field of the Invention
The present invention relates to a drive device for an optical disc apparatus for recording on or playing a CD, DVD, BD (Blu-ray Disc), or other optical disc.
2. Description of Related Art
Optical pickup feeding devices provided in drive devices for general optical disc apparatuses comprise a lead screw and a resin tooth that is advanced following the rotation of the lead screw while being in meshed engagement with the lead screw. The tooth is further attached to an optical pickup that can move along a guide shaft, is extended in a cantilevered state in a direction orthogonal to the axis line of the lead screw, and is provided with a tooth spring for elastically urging the tooth from a back part and urging meshing cogs thereof in the direction of meshing with the lead screw. Various improvements to the mechanisms of such optical disc apparatuses have also been proposed in recent years.
For example, there is disclosed in Japanese Laid-open Patent Publication No. 2008-257826 a configuration of a feeding apparatus for an optical pickup comprising a lead screw and a resin toothed body that is advanced following the rotation of the lead screw while being in meshed engagement with the lead screw, the toothed body being attached to an optical pickup that can move along a guide axis adjusted at a slant, extended in a cantilevered state in a direction orthogonal to the axis line of the lead screw, and provided with a spring body for elastically urging the toothed body from a back part and urging meshing cogs thereof in a direction of meshing with the lead screw; wherein the position of urging the toothed body by the spring body in relation to the position of meshing between the meshing cogs of the toothed body and the lead screw is offset toward the free end of the toothed body and away from the meshing position.
There is disclosed in Japanese Laid-open Patent Publication No. 2005-216344 a configuration of a rack for an optical pickup module provided with a rack body and a contact part for contacting a lead screw shaft, and used so that an optical pickup for irradiating an optical disc with laser light and recording and replaying information moves in the radial direction of the optical disc; wherein the contact part and the rack body are disposed facing each other with an elastic member provided therebetween, and a substantial parity is achieved between the deformed shape of the elastic member when an upward external force is applied to the contact part and the deformed shape of the elastic member when a downward external force is applied.
There is disclosed in Japanese Laid-open Patent Publication No. 11-224469 a configuration of an information recording apparatus comprising holding means for holding an information recording medium; readout means for reading out or reading/writing information on the information recording medium; guiding means for holding the readout means (or the holding means) while allowing the readout means to slide parallel to the information recording medium; feeding means for moving the position of the readout means (or the holding means) in a sliding direction to vary the position at which the information on the information recording medium is read out, or to vary the position at which the information is read/written; and a chassis for supporting the holding means (or the readout means), the guiding means, and the feeding means; wherein the feeding means comprises a lead screw formed having a spiral groove on a cylindrical surface and disposed parallel to the guiding means, driving means for rotatably driving the lead screw, and transmitting means provided to the readout means (or the holding means), engaged with the spiral groove, and adapted to transmit driving power from the lead screw to the readout means (or the holding means); the transmitting means comprises a cog part that slidably engages with the spiral groove on the lead screw on the side near the guiding means, an attachment fixed to the readout means (or the holding means), and engaging means constructed of a hinge part connected to the attachment so as to allow the cog part to be engaged with and disengaged from the spiral groove; and the toothed part comes into contact with any of the guiding means, the readout means (or the holding means), the attachment, or the chassis to restrict the amount of displacement of the cog part before the engagement between the cog part and the spiral groove is released when the cog part is displaced in the direction of disengagement from the spiral groove.
It is apparent that thinner teeth will be required when an attempt is made to make thinner drive devices in order to respond to the current demand for smaller optical disc apparatuses. However, a decrease in tooth thickness is not discussed in the aforementioned three cited references. A problem therefore arises in that simply reducing the thickness of a conventional tooth will fail to meet the design requirements. Examples of the design requirements include preventing the tooth from breaking due to stress applied to the tooth when the tooth spring is inserted during assembly, ensuring adequate displacement of the tooth when the tooth is urged toward the lead screw, and preventing the tooth from breaking when tooth jumping occurs.